A 62-year-old woman, who had hit the left frontal part of her head on a door three years ago, noticed a small tumor on the particular site, and the tumor gradually increased in size. In gross appearance, the resected tumor was a dark-red hematomalike protruded mass covered by a white capsule. A histological examination revealed a fairly well-defined tumor consisting of a multilocular cystic structure containing blood and proliferation of histiocyte-like cells with pseudovascular spaces embedded in the thick and sclerotic fibrous stroma. Some foci of fascicular proliferation of fibroblast-like spindle cells were also intermingled. The lesion was diagnosed as aneurysmal fibrous histiocytoma based upon the histological and clinical findings. Angiomatoid malignant fibrous histiocytoma and chronic expanding hematoma are considered to be important differential diagnoses in our case.
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